1. Field of the Invention
Described herein is an insulating film of a metal oxide containing hydrogen and a metal, and a semiconductor device including the insulating film.
2. Related Art
To secure the charge to be induced at the channel of a MISFET (metal insulator semiconductor field effect transistor), the gate insulating film is normally made thinner, and the capacity is made larger accordingly. As a result, the SiO2 film as the gate insulating film has become thinner, and at the present, it is now as thin as 1 nm or less. However, there is a large gate leakage current in the SiO2 film, and the power consumption cannot be restricted to an allowable amount due to wasting of standby energy. For example, a 0.8-nm thick SiO2 film has a gate leakage current as large as 1 kA/cm2, and the large power consumption presents a serious problem.
To reduce the power consumption, it is effective to increase the film thickness. Therefore, the use of an insulating film made of a high-k material that can maintain a sufficient charge amount even if the film thickness of the insulating film becomes thicker than that of the SiO2 film is being considered. Various kinds of metal oxides have been known as stable high-k materials. The most promising materials for the insulating films having such characteristics include HfO2, ZrO2, silicates of those materials (HfSiO and ZrSiO), aluminates of those materials (HfAlO, ZrAlO), and LaAlO3.
However, a high-k metal oxide tends to contain oxygen defects, as will be described later. Therefore, large current leakage often occurs due to the oxygen defects, and the reliability becomes poorer.
High-k oxynitrides (HfON, ZrON, HfSiON, and ZrSiON) are also expected to be used for the gate insulating film. However, with a small amount of nitrogen, crystallization occurs in the insulating film, and the insulation characteristics are degraded. Therefore, it is necessary to add a large amount of nitrogen. When a large amount of nitrogen is added, however, as described hereinbelow, more oxygen defects are caused due to the introduction of nitrogen, and large current leakage occurs. As a result, the reliability becomes poorer. If nitrogen exists in the vicinity of the interface between the substrate and the insulating film, fixed charges are generated, and the interfacial structure is disturbed. Therefore, it is preferable to form a structure in which nitrogen is located at a distance from the interface between the substrate and the insulating film (JP-A 2005-353999 (KOKAI)).
As described above, in a case where a high-k oxide or oxynitride is used for the insulating film, oxygen defects are easily formed, and large current leakage occurs due to the oxygen defects. As a result, the reliability becomes poorer.